I have been using a silicone spray on my chain, but it isn't long before it rusts.
What about about Squirt Long Lasting Dry Chain Lube ?
We don’t give specific product recommendations but the following general advice should help reduce rusty chains:
don’t store your bike outside. If you do, put it under a breathable cover. Morning dew is a considerable source of moisture so check your bike in the early morning to see if it’s wet.
wipe down your chain after it gets wet. Having a dedicated shop rag for your chain helps
if your oil-based chain lube washes off too easily, try a wax-based lube or vice versa. Ask the staff at your local bike shop what they recommend for your local climate and terrain
if all fails, try a chain that has corrosion resistance as a feature. Note that nothing is corrosion proof and you’ll still have to do all of the above
Or, accept that some degree of rust is part and parcel of having a working bike (as opposed to a display bike), note that rust only accumulates on the non-moving and non-wearing side plates of the chain, keep it lubed where it matters (internally on the bearing surfaces) and be happy.
There are four ways to reduce rust:
Keep water away. Dry storage of the bike, ride only in sunshine, you get the idea...
Keep water from the metal. Use an oil that thoroughly sticks to your chain, and the water will have a hard time to reach the iron. Wax or fat may be even more effective in keeping water away from the chain, but they attract dirt to the chain like hell.
Move the chain. Rubbing metal on metal constantly removes any rust before it becomes a problem. However, the movement needs to be frequent enough. A week in the rain without moving, and your chain is one piece.
Use stainless steel. You can buy chains made from stainless steel, and in my opinion, they are well worth the extra dollars.
To me, the most painless solution is the last. Of course, it's still a good idea to keep it well oiled...
One of my bikes lives outdoors 24/7 in all weathers (in a rainy country). It's cheap and not very attractive, so I'm concerned with rust that affects the workings more than rust that affects the looks.
On this bike, I use GT85 (light spray oil with PTFE) for the chain and derailleurs. I take the chance to oil it when it's dry, which isn't all that often in the winter. The chain maintains a dull grey colour (typical of exposed steel), rather than a rust colour, so long as I don't leave it too long. A light spray of oil over the sprockets keeps them from rusting too much as well. It's only ridden on tarmac, and is never cleaned, because it shuttles between the station and work and never goes home). I tried a corrosion-resistant chain on this bike (or its predecessor) and found it to rust quite quickly when I forgot to oil it.
If you're interested in looks, stainless is the way to go, but stainless is less tough than normal chain steels.
I think rust is a symptom of insufficient chain lube and not a problem in and of itself. A bit of superficial rust won’t harm a chain but insufficient amounts of lube will significantly increase friction and wear.
Regularly apply lube, make sure to wipe the chain clean before and after lubing. Use dry lube for dusty conditions and wet lube for wet/rainy conditions. How often you have to re-apply lube depends on conditions as well. A single ride in bad weather can be enough to make re-lubing necessary.